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787 Crosswind Testing and Update on Suborbital Flight

This post is an update of two unrelated topics: first, the recent flight testing of the Boeing 787 Dreamliner, with references to the Airbus A-380, and, second, the future of suborbital flight starting with space tourism possibly followed years later by suborbital public transport.

Let’s start with the Boeing Dreamliner which is already a test pilot’s dream come true, as the first video shows. Needless to say: an airliner’s capability to sustain high crosswinds on landing is a feature airlines look for in their decision to purchase or lease a fleet of new aircraft. In fact, any airliner having to divert to an alternate airport due to excessive crosswind on the destination runway is a major annoyance for both the airline and its passengers.

Keflavik Airport in Iceland has the dubious distinction of having some of the strongest crosswinds. No wonder Airbus and Boeing, to name but two aircraft manufacturers, call Keflavik Airport a testbed for exploring a new aircraft’s landing and take-off limits in demanding wind conditions.

YouTube has dozens of genuine videos, other than the ‘Flight-Sim’ kind, showing the crosswind landing capabilities of new aircraft. The crab angle of sky giants such as the Airbus A-380 on final approach and touch-down seems almost unreal. At times, the Airbus looks as if it were flying sideways. Later on, at the 2009 “EAA AirVenture Oshkosh” event, a visiting A-380 on a public relations tour created a sensation when landing at Oshkosh in a hefty crosswind. There was no shortage of knowledgeable commentators on location to describe the sort of heavy footwork going on in the cockpit and other corrective input by the flying pilot in order to maintain the A-380 lined up with the runway’s centre-line on approach, right after after touch-down and during initial roll-out.

Such sights have onlookers wondering whether the aircraft is on auto-land or hand flown. Which of the two produces the smoothest results? Unfortunately I do not have the answer for now. Suffice it to say that one of the many difficult crosswind landing of Boeings 747 aircraft engaged in actual commercial flight can be viewed on YouTube. One can appreciate the severe lateral stress on the landing gear upon touch-down. In such landing conditions, the aircraft jerks on touch-down with the main landing gear billowing heavy smoke from its tires. Less frequently, aircraft display an unusual wing-low attitude on approach before levelling the wings, and a very noticeable crab angle above the runway, followed at times by an immediate go-around. Go-arounds in stiff cross-winds are presumably more frequent in the case of jetliners having a tall landing gear, such the defunct Concorde.

Speaking of using a wing-low technique in the final stage of a cross-wind landing, several twin jets, including the Boeing Dreamliner, powered by turbofans engines with a wide diameter and slung below the wings, would be nearly impossible. Not only are the turbofan engines much larger in terms of cross-section, but their landing gear is also short for the overall size of the aircraft. This is where, IMO, the Airbus A-380 shines with its gull-wing design that helps keep the engines well above the runway upon touch-down, despite the short undercarriage and the impressive wing flexing on touch-down. Notice for example, in the video linked above, showing the Airbus A-380 landing at Oshkosh in 2009, the busy foot-work by the FP (flying pilot), as displayed externally by the rudder movements. These control inputs are naturally necessary, even after touch-down, in order for the heavy aircraft to remain on the runway centreline during initial roll-out, in cross-wind gusts reported to be 23 kts. These are only part of the challenging conditions the A-380 and the Boeing Dreamliner have been designed and tested for prior to production.

Despite the benefit of allowing large turbofans a higher clearance above the runway on landing, both the Dreamliner and the Airbus A-380 are designed to take severe punishment in a cross-wind landing without the landing gear collapsing due to lateral drift, or any engine and wing tip scraping the runway. Heavy airliners have their own constraints in stiff cross-wind landings, for touching down safely on a runway, wings level, compared to good old propeller-driven tail-draggers which are capable of touching down, in cross-wind conditions, on their upwind main gear alone until bleeding enough airspeed for a full three-point contact with the runway.

No lateral drift of the Boeing Dreamliner appears during video-recorded test flights in heavy crosswinds approach and landing at at Keflavik Airport. Is this a reflection of a test pilot’s superior flying skill? I can’t say for sure. The video of the Dreamliner’s crosswind landings linked below indicates that some of the landings in heavy crosswind are carried out in auto-land mode. Presumably, they must be able to do so in order to meet current certification requirements.

Here is a video of the Dreamliner’s crosswind testing , complete with a running commentary by a Boeing official and test pilot.

I thougt it would be useful to include a similar video below, showing the Airbus 380 undergoing the same rigorous testing in strong cross-winds and on a wet runway. If only one could better see the rudder and aileron deflections that keep the large A-380 in line with the runway on approach. No aircraft is a master of the sky, and yet both the Boeing Dreamliner and Airbus A-380 seem very stable and undaunted, from a distance, during strong crosswind approach, touch-down and initial roll-out.

Our second topic below is an update of the Virgin Galactic project mentioned in a previous postin this blog, concerning the demise of the Concorde supersonic airliner. The main question raised in the earlier post was what sort of supersonic vehicle would likely fill the void left by Concorde in supersonic air transport. It was mentioned at the time that Virgin’s Galactic suborbital flight project was an attractive proposal. The video below indicates that suborbital public transport is years away. For now, suborbital flights to be conducted jointly by Virgin Galactic and its main partners will cater to space tourists only. The space tourism concept implies that any suborbital spacecraft launched from the mother ship will return for landing at the spaceport of departure.

Sir Richard Branson and his partners plan 1) to make suborbital flights more affordable over time, for the benefit of space tourists without deep pockets, and 2) ultimately, to develop the global infrastructure – a major challenge to take on, as existing airports are not suited for such flights – and to redesign suborbital spacecraft necessary to achieve intercontinental public transport. Whether suborbital flight will in fact meet the need for affordable supersonic transport remains to be seen, of course, despite the enthusiasm displayed presently by its proponents. Yet, more conventional SST technology should not be discounted since improved and safer versions of Concorde might see the light of day before suborbital flight has sufficiently matured to meet the need for affordable intercontinental supersonic public transport.

The following BBC report highlights Branson’s plans for suborbital flight:

More information on the alternate application of SST technology, such as an improved variant of Concorde for instance, will follow as relevant material is found.